Transmission system



'Dec. 12, 1933. F, CONRAD TRANSMISSION SYSTEM Filed Jan. 17, 1930 4 Sheets-Sheet l ATTORNEY Dec. 12, 1933. CONRAD 1,939,042

TRANSMISSION SYSTEM Filed Jan; 17, 1930 4 Sheets-Sheet 2 Z HVET, 9.

INVENTOR jz'mv% Carr/yd A'TTORNEY Dec. 12, 1933. F. CONRAD 1,939,042

TRANSMISSION SYSTEM Filed Jan 17, 1930 4 Sheets-Sheet 5 dzzmva. 5232 42768.

INVENTOR 3 2 way (Zn/22a,

ATTbRNEY Dec. 12, 1933. F. CONRAD 1,939,042

TRANSMISSION SYSTEM Filed Jan. 17, 1930 4 Sheets-Sheet 4 r I; 1 770/174 \f 5 A: a ,(X/s

INVENTOR fray/ (Br/rad:

' ATTORNEY Patented Dec. 12, 1933 UNITED STATES TRANSMISSION SYSTEM Frank Conrad, Pittsburgh, Pa., asslgnor to Westlnghou'se Electric -& Manufacturing Company, a corporation of Pennsylvania Application January '17, 1930; Sean No. 421,471

Claims.

My invention relates to a transmission means and, more particularly, to an antenna system and a method of transmitting radio signals.

When referring to radio waves we frequently a consider them as comprising two waves, a ground waveand sky wave, the sky wave being that portion of the wave received by reflection from the Kennelly-Heaviside layer and the ground portion being that portion which follows along'the earths surface in itstravel from the transmitter to the receiver. These terms will be used throughout the following descriptionin explaining the'objects and purposes and the manner of operation of my invention. In using a verticaltransmitting antenna, the local signal is due to the radiation 'of the ground wave component of the transmitted wave,'whereas distant signals depend considerably on the sky wave component or, in other words, the radiation initially at an angle of elevation, this vertical component subsequently descending as it moves outward from the antenna by. reason of reflections from Kennelly-Heaviside layer, and also by reason of the fact that the waves travel slower at the surface of the earth than in the upper atmosphere.

The pattern of a single vertical transmitting antenna is a circle, points at equal distances from the center of which representing substantially 80 circle. In order to secure or obtain greater intensities at distant receiving stations, it will be necessary to increase the power output or the power generated at the transmitting station. However, this will also result in a great increase in the local intensities or localsignal strength which is both undesirable and unnecessary.

As is well known to those who are acquainted with the operation of receiving sets, broadcast reception is much more eflicient during the evening than during the day by reason of the fact that lower strata of atmospherebecome ionized during the day and the radio waves are more or less absorbed. This absorption reduces the eifect of the vertical component or sky wave, and reception during the day arises mostly fromthe' ground wave.

It is an object of my invention to attain an increase in the distant Signal strength without increasing signal strength in the vicinity of the broadcasting station.

It is another object of my invention to extend the range ofinfluencejof a vertical component of 66 a transmitted wave whereby radio reception in the same field intensity. In the vertical plane the magnetic field may be represented by a semithe evening may be extended to greater distances.

Another object is to extend the influence of the ground wave or horizontal component fordaylight transmission. A further object of my inventionis to provide means for selectively extending the influence of either the vertical component or the horizontal component of a transmitted wave.

An additional feature of my invention resides in the method for accomplishing the above results.

Further features of my invention will be disclosed inthe following description taken in conjunction with the accompanying drawings, wherein 7 Figure 1 represents a field intensity pattern in the horizontal plane, for a single vertical transmitting antenna. 7

Figs. 2 through 8 represent field intensity patterns in the horizontal plane for an antenna system involvingmy invention utilizing four vertical antenna operating in synchronism for various spacings of the antennae.

Fig. 9 represents a field pattern in a'horiz'o'ntal plane for a single vertical antenna, and for eight vertical antenna operating in sychronism.

Fig. lo'represents a fieldpattern in a vertical plane for a'single vertical antenna, and for eight vertical antennae operating in synchronism.

Fig.11 shows a curve illustrating field intensity at a constant distance in vertical'and'horizontal directions about four vertical antenna: withcurrents in adjacent antenna: out of; phase.

Fig. 12 is a curve showing field intensity at a constant distance in vertical and horizontal planes about eight vertical antennae with currents in adjacent antennae 45 out of phase Figs. 13-and 14 are diagrams illustrating the mathematical basis for my method of transmitting.

Fig. 15 illustrates schematically a four antenna system embodied in my invention.

It the ratio of horizontal radiation 'to the radiation of thevertioal component can bedecreased then the desired decrease of the ratio of local'to distant signal strength may be attained. Broadly speaking, this is accomplished by using an arrangement and spacing of a plurality of vertical antennae-fed with currents from'a transmitter; the currents in the antennae being in time phase. In an arrangement of this order interference betweenwaves from the various antenna: will reduce the horizontal fieldstrength and in this'manner cut down the radiation resistance of the antenna system in a horizontal direction.-

' ferent directions.

This will result in an increase of current to the antenna with a corresponding increase in the vertical component of the wave to such a value that the energy output from the system will be substantially the same as. when using a single vertical antenna. This can be accomplished by running a transmission line 6 (Fig. 15) to a central point '7 and running feeders 8, 9, 10 and 11 from this point to the individual antenna 12, 13, 14 and 15. It will thus be obvious that the influence of the vertical component has been greatly extended without increasing local signal strength.

To illustrate the above feature, calculations were made of the field intensity inthe horizontal plane in different directions from four vertical antennae in which the currents were maintained in the same time phase and the antenna: were located on corners of squares of diiierent dimensions to determine how much the interference betweenthe transmitted; waves reduced the horizontal component. The patterns obtained, aswell as the pattern for a single antenna with the same total current, are plotted to the same scale in Figs 1 to 8. The calculated values from which these patterns were plotted are set forth below:

Table 1 Field intensity Area f intensity Noi oi Side of Diameter squared 0 es s uare o cu-c e proporp q tional to energy Meters Meters -1 0 A 0 4 4 2, 500 4 3535A 5 A 2 178 120 4 4375A 619k 172 066 15 4 5 x 707x 163 .008 6 4 .531) .751 .110 .023 .6 4 547 k 775). 070 015 1 4 .562 .795X .059 .015 .04 4 q .625 k .885). 125 .009 12 The patterns represent field intensities, whereas the last column in the tabulated values represents the area of the patterns squared, which values are proportional to the energy output of the antenna system in the horizontal plane. The results show that the minimum horizontal radiation occurs whenthe four poles are on the corners of a square .562 on a. side.

- Testsmade at 40 meters for a four antenna system indicate that intensity patterns similar to those calculated are obtained and that there is a noticeable increase in distant signal strength when the transmitter is shifted from a single antenna to the four pole antenna system. 1 For the condition of minimum horizontal radiation with four antennae the intensity, as clearly illustrated in Fig. 7, varies considerably in dif- To obtain a more nearly circular intensity pattern calculations were made for an eight antenna system. A representative pattern obtained for the eight antenna on a circle of diameter .707). meters is shown in Fig. 9 to the samescale as Fig. 1. The horizontal distri-- bution of intensity is illustrated by the cornercurve 1-for the eight pole system, and by the outer curve 2 for a single pole system. Calculations were also made for an eight antenna systemto determine the vertical component. The general shape of the intensity variation in a vertical plane is shown in. curve 3 Fig. 10, together with the curve for the single vertical antenna carrying the same total current as the eight anponent to the horizontal component.

tenna system. This figure clearly shows the increased ratio of radiation of the vertical com- It should be realized that when used with a transmitter the total current in the eight antenna system will not be the same as with the single antenna, but will be considerably larger in the case of the eight antennae due to the decreased radiation resistance. Therefore, the radiation in the vertical direction should be larger and that in the horizontal direction should, if anything be smaller for the eight antenna system, than for the single antenna. The dotted line curve 5 of the figure illustrates this difference, when compared with the curve for the single antenna 4.

. For daytime broadcasting it is desirable to obtain the reverse effects, namely, a strengthening of the horizontal component of the transmitted component. This result can be accomplished by using an arrangement of vertical antennae substantially as described above,v and throwing the currents in each pair of diametrically opposed anteimaa approximately 180. out of phase. This will result in a suppression to a certain extent of the vertical component-and an .increase in the strength of-the horizontalcomponent. For instance, one could use four vertical antennae spaced equally on a circle of diameter in the neighborhood of M2, with currents in the diagonally opposite poles 180 out of phase and the currents in adjacent poles 90 out of phase. The intensity of the radiation in a given direction in the horizontal plane is equal to'the vector sum of the intensity produced by the individual antennae. This intensity can be represented by the following formula:

where C=velocity of propagation, T=time; S=distance from center of antenna system;- AS1i=SnS=appr0x. r cos a; and n=time phase lag of current behind phase of reference. For phase of reference let (IT-8:0; then lag of antenna field behind phase of reference is 1' cos a+4 n. Each antenna will have an in-phase. 15.115 component H cos n and an out-of-phase com-- ponent H sin 4m. Resultant field The intensity of the radiation in a verticalplane at an angle 3, for instance, for a four antenna systeminaybe, calculated in the following manner, with reference to Fig. 14 of the drawing.

' 1,030,042 :The equation for a single vertical antenna inv a directionat an angle or elevation where h=effective height; I,=current at base of antenna; x=wave length: S=distance from antenna; and fl=angle oi elevation. For a system of several antenna, phase relation must be taken into account. The phase relation is given by where C=velocity of propagation; T=time, S=distance from center of mtennav system. ASn= S.-S=(approx. X cos ;8)=r cos (1 cos p; (aangle in horiz. plane of antenna from X axis; and n=time phase lag of current in antenna behind phase of reference. For relative phase relation let (IT-8:0 so that angle of lag of antenna field behind phase of reference is Each antenna will have an in-phase component H cos 4m and an out-of-phase component H sin m. The resultant field where the summation ls algebraic addition.

Consider the field arising from the four pole system above, in the direction of a diagonal.

2 H sin Then the two poles on the other diagonal will tenna with the same total current. At an angle of degrees the effective distance phase difference is cos 60 180=90; therefore the signals from the two latter antennas are out of phase and the vector sum is equal to 1.414

.3535 times the signal in a single pole with the same total current. For directions between two poles the radiation is slightly greater than in the direction of a diagonal, but the relative proportion of horizontal and upward radiation is the same.

Thus the radiation resistancehas been reduced to less than half that of a single antenna, sothat if the ohmic resistance is small compared to the radiation resistance, the current in the four pole system would actually be about twice that in a single pole antenna giving a horizontal radiation greater than the single antenna and an upward radiation less than the single antenna. An eight pole system with currents in adjacent poles 45 out of phase has the advantage over the four pole system just described in that it gives slightly greater horizontal radiation for the same total current; that is, it reduces the horizontal field less for the same total current; and in that it gives a circular field pattern.

The phase relationships assumed above can be obtained by making the transmission lines 12,

X=distance in direction of X-axls, of antenna pole from center of system. X-axis in this figure corresponds to line S in the figure for the horizontal plane.

13, 14, 1 5 to the individual antenna: of dliferent length or by loading the lines by diiferent amounts, preferably keeping the surge impedances approximately the same.

It'is evident that the same antenna systemcan be used. with either of the above schemes, and that with two separate transmission systems and remote control switching, it would be possible to change rapidly from one to the other. j

While I have described my invention'as embodied in antenna systems comprising tour antennm and eight antennae, it is obvious that any number of antennae might-be used with similar results and I do not wish to be' limited to the specific details outlined above only'insofar as my invention may be limited by the prior art.

I claim as my invention:

1. In a system for radiating electro-magnetic energy eight vertical antennae, said antennae being substantially uniformly disposed on the circumference a circle of diameter substantially .707 of the wave length of the energy to be transmitted and means for energizing said antennae cophasely.

2. The method of transmitting electro-magnetic signals with a system incorporating eight vertical antennae arranged at the vertices of a regular octagon which comprises impressing periodic electro-magnetic disturbances, with a phase displacement of 45 between successive antennae, on said antennae.

3. The method of' transmitting electro-magnetic signals with a system incorporating 1!. Vertical antennae, said antenna being disposed at the vertices of a regular polygon which comprises impressing periodic electro-magnetic disturbances, with a phase displacement of between successive antennae, on said antennae wherein n is the number of said antennae.

4; The method of transmitting electro-magnetic signals with a system incorporating a plurality of vertical antenna, said antennae being disposed at the vertices of a regular polygon which comprises impressing periodic electro-magnetic disturbances, with a phase displacement of. 180 between antennae displaced by an angle of 180 on said antennae.

5. In a system for radiating electro-magnetic signals, four vertical antennae disposed substantially at the vertices of a square of which the sides have a length of substantially .562 of the wave length to be transmitted and means for energizing said antennae cophasely.

6. In a system for radiating electro-magnetic signals, four vertical antenna disposed at the vertices of a square of which the sides have a length of greater than .547 of the wave length to be transmitted and less than .625 of the wavelength to be transmitted and means for energizing said antennae cophasely.

7. The method of broadcasting electro-magnetic signals with apparatus of a type incorporating eight vertical antennae disposed at the apices of a regular octagon which comprises the steps of impressing periodic electro-magnetic disturbances during the day time cophasely on each of said antennae, and impressing disturbances, with a phase displacement of 45 between successive antennae on said antenna: during the night time.

8. In a system for radiating electro-magnetic energy, eight vertical antennae, said antennae being substantially uniformly disposed onthe cir-'- cumference ofa circle of diameter substantially .707 of the wave length of the energy to be transmitted, and means for alternatively energizing said antennae cophasely or with a phase displacement between successive antennae of 45.

9. The method oft/broadcasting electro-magnetic signals with apparatus of a type incorporating n vertical antenna: arranged at the apices of a regular polygon having n sides, which comprises the steps of impressing periodic electromagnetic disturbances cophasely on said antenna during certain periods of the day and impressing dis-' turbanc'es, with a phase displacement 01' ing the night time.

between successive antenna: on said antenna: dur

FRANK CONRAD. 

